The present Application claims priority from Korean Patent Application Number 10-2002-0038054 filed in the Republic of Korea on Jul. 2, 2002, which is incorporated in-full herein by reference.
1. Field of the Invention
The present invention relates to a projection lens system applied to a video image projection apparatus, and more particularly to a projection lens system for improving an aberration correction factor to implement images of high resolution and high luminance.
2. Description of the Prior Art
Recently, the demand for image display devices larger in size and of higher quality has increased. Accordingly, image projection that enlarge and project small images by using projection lenses are rapidly becoming popular. Such image projection apparatus are mainly classified into front projection apparatus and rear projection apparatus based on projection methods.
Front image projection apparatus employ a method projecting a video signal from the front of the screen, which are generally used in movie theaters, conference rooms, and so on, whereas the rear image projection apparatus employ a method projecting a video signal from the rear of the screen, which has been popularized in the form of projection TV. In particular, the rear image projection apparatus can display relatively bright images even in bright ambient environments, so they are used more compared to the front image projection apparatus.
FIG. 1 is a view for showing a general rear image projection apparatus.
In FIG. 1, a rear image projection apparatus 100 has a light source 110, a panel 120, a projection lens system 130, a mirror 140, and a screen 150.
The light source 110 generates and emits light by using halogen, xenon, and so on. The panel 120 is a display device producing images by using light emitted from the light source 110. A cathode-ray tube (CRT), a liquid crystal display panel (LCD), a digital micromirror device (DMD), or the like is used for the panel 120.
The projection lens system 130 enlarges and projects the images produced on the panel 120 in a predetermined magnification power. The projection lens system 130 includes plural plastic lenses or glass lenses. That is, the magnification power of the projection lens system 130 is determined by the plural lenses.
The mirror 140 creates the total reflection of enlarged images projected from the projection lens system 130 toward the rear of the screen. The totally reflected images are focused on the screen 150, by which a user can view the images focused on the screen 150.
However, in the conventional rear image projection apparatus 100, the projection lens system 130 has plural lenses, causing a problem that raises the cost of the rear image projection apparatus 100 and makes it difficult to manufacture the rear image projection apparatus 100 thin. However, the number of lenses is reduced in order to solve such a problem, causing a problem that the quality of images displayed on the screen 150 is entirely deteriorated by aberration, distortion, and so on.